fact or fiction (LiFePO4)

[T1 Terry]

A g m has had a chew on it .
Bernie .

A string of it got posted up on the private lithium forum. If it wasn't so serious it would be laughable, he really doesn't have a clue what he's talking about. It seems he read some nonsense he liked somewhere on the interweb, embellished I a bit more to suit his sales pitch, then posted it over there as fact. So much for their no sales pitching or you'll be banned stuff, it seems to depend if you follow the line of thinking the admin person has, then it's ok to post it, it will be removed and you'll get banned if it goes against the barrow they want to push.

T1 Terry

[BruceS]

Terry you're going to love this one!!
AGM has finally backed you up even if not mentioning you!!
Pity I can't post there any more!!

Stormy2 wrote: ↑
Sun Jun 16, 2019 9:39 pm
For that, they obviously are hiding something just like VOLTECH are.
AND THEN AGM RESPONDED .....
And the most obvious things many 12V LFP batteries hide are....the cells themselves including their BMS.
And there will be ramifications of this down the track.
Since lithium cells aren't self balancing, the battery pack relies on the internal BMS to perform this task.
With no access to cells and BMS we just don't know if the BMS is doing what it is supposed to. We just hope it'll be able to keep all cells nicely top balanced by overcoming different self discharge rates between individual cells.
When looking at a number of cheap BMSes (don't expect anything else in a low cost battery), their balancing ability is limited to a few tens of milli amps which I've found to be inadequate.
The problem is made worse by some lithium chargers set to dial back the charging voltage well before the pack is fully charged although adequate charging voltage and time are prerequisites for this kind of balancing.
And with no balancing the worst cell (the one with the highest self discharge rate) will acquire a slowly decreasing SOC making it subject to top memory. Top memory in an LFP cell masks a lower SOC with a higher voltage.
Now we have two effects causing the troubled cell falling behind, higher self discharge, and accumulating top memory.
Because the cell shows higher voltage yet depressed SOC, if it reaches the top, it'll be drained by the BMS during top balancing, lowering its SOC even more (the BMS uses cell voltage as a proxy for cell SOC).
Needless to say, total available battery capacity will take a hit by a cell's SOC falling behind with no way to remedy the situation.
To erase the accumulated top memory the troubled cell needs to be charged to an elevated voltage level and kept there for some time. Impossible to do without access to individual cells.
At the very least, there should be a cell service port bypassing the BMS, better yet full physical access to all internal components.
What I've found really worthwhile having for instance, is a well designed BMS allowing monitoring by smartphone to a high degree of accuracy/resolution (think milliVolts) of individual cells during the final stages of balance charging through the service port up to 3.65Vpc (14.6V).
Battery Supplier
http://www.batteryvalue.com.au

[Mrcoolabah1au]

Are u banned to Bruce is the caravan forum u are talking about

[BruceS]

Yeah! I'm from Mannum.... haha
Called a spade a spade once too often! (I thought it was a shovel!)

Like this Ray?
To "call a spade a spade", or, "to call a spade a shovel" are both forms of the figurative expression which requests that the speaker should call, or has called, a person, place, or thing, by the most suitable name it could have without any reservation to the feelings or strained formalities that may result from its ...

[T1 Terry]

I'm guessing "Battery Value" is AGM's business name and therefore his website. It seems he has access to some of the stuff I have posted in a number of places, it could even be off Margaret's website for all I know, I still haven't read it
There are a number of articles on his site that aren't direct copy and paste, but exactly what I've said else where just rewritten a bit.
It is good to see he has finally realised there as definite issues that must be addressed when using lithium batteries, I wonder if it has come as a result of a few of his longer term battery test packs he has spoken about before in previous posts.
The more this knowledge gets out there, the better for everyone. There will be many people with seriously damaged wallets in the not too distant future, I was informed over on the Grey Nomad forum that a caravan supplier who was fitting 2 x 100Ah lithium batteries and a Redarc BMS in 2018 has changed to a single 200Ah battery and system from Chris at Enerdrive. I don't know if Chris monitors cell voltages or not, he might monitor half pack voltage that would be at least a step in the right direction, still open to problems in an individual cell, but at least it is some sort of warning system that something has gone wrong. The down side if their whole battery assembly is locked up in a case, it must be sent back to Enerdrive if there is a problem.
The advantage of our build method is all the warning alarms and we can talk you through a test procedure if a problem should arise and get you out of trouble no matter where you are ... well as long as you can climb a hill to get telephone or internet access if you really are that far off the beaten track. Most of the issues are handled in the info pack Margaret supplies with each install, but every so often we get one out of left field. Fortunately I know the systems well enough to sort the problem with a bit of feed back from a few tests.

T1 Terry

[Mrcoolabah1au]

Yes have a few minor issues but I have only been small and it is easy fix be turning on something to drain the amps ⛑